| With the rapid development of the social economy and technology, China’s nationalcomprehensive strength is enhancing greatly, and the various types of construction project arelarge in number and scale, including water conservancy and hydropower projects, mineralresources exploitation projects, traffic carriage projects, oil and gas transportation projects,industrial and civil architectural projects and so forth. During these projects constructing,there are some bad effects appearing. Firstly, construction projects destroy and disturboriginal underlying surface. Secondly, large amounts of waste soil and residue is producedbecause of excavation and embankment volume, construction time, material quality, dividingbid sections, transportation distance and many other factors. Large amounts of waste soil andresidue can easily cause high intensity, wide range, great harmfulness soil and water erosion,which severely endangers water and land resources and natural environment of human beings.These soil and water erosion would be a threat to social development, ecological security andpeople’s life and producing. However, there were obvious differences in disturbanceunderlying surface by engineering activity and original underlying surface of the soil andwater erosion. Underlying surface disturbed by engineering activity represents differentintrinsic mechanism and external features from original underlying surface. Hazards ofman-made soil and water erosion from underlying surface destroyed by engineering activityattracts the attention of the whole society and governments.This thesis takes various types spoilbank in construction projects as the main object ofstudy. Both route investigation and typical investigation methods were applied to collect dataon spoilbank produced in point projects and line projects from Dongbei plain, Huanghuaihaiplain, Guanzhong plain, Qinba mountain area, red soil hilly region of Jiangxi, mountain areaof Guizhou. Investigation should consider several factors: spoilbanks locating in water soiland water erosion region, plain hilly and mountain geomorphic types and soil types. Based onthe complexity and diversity of spoilbank, we explore common characteristic in accumulationtype, material composition of underlying surface, slope shape factors in the various types ofconstruction project at different topographic and geomorphic areas. According to methods of man-dumped and accumulation shapes, classification systems of spoilbank in constructionproject were generalized. Classical theory of statistics were applied to determine simulationmodels standardized parameter of underlying surface for laboratory test. Different types ofspoilbank underlying surface’s soil erosion were simulated in inner-door rainfall experimentalcondition. These studies results provided scientific basis for revealing characteristics ofspoilbank soil and water erosion in construction project, seeking the calculation model ofspoilbank soil and water erosion and prevention and control measures. Main conclusionsshowed as follow:(1) According to methods of man-dumped and accumulation shapes, construction projectspoilbank were generalized into five categories: conical scattered accumulation, dumpedalong the slope, layered compaction and scattered accumulation on the top of slope, dumpedaccumulation in strips, rolling compaction by construction machinery at the top of slope.(2) Based on the results of laboratory tests, the theory of statistica was applied to analyzecomposition of slope surface. The results showed as follows: The percentages of stones andsoil aggregates (particle diameter>10mm) at different position of spoilbank slopes in Qinbamountain area and mountain area of Guizhou were greater than spoilbank in other studyregion; The percentages of gravel and consolidated soil, coarse-grained soil, medium soil(particle diameter<10mm) at different position of spoilbank slopes were less than spoilbankin other study region, indicate the share of coarse-grained material at different position ofspoilbank slopes in Qinba mountain area and mountain area of Guizhou were greater thanspoilbank in Dongbei plain, Huanghuaihai plain, Guanzhong plain and the red soil hillyregion of Jiangxi.The percentages of fine-grained soil in six study regions were all less than3%; Stonesand soil aggregates’ gravity separation effects were obvious in six study regions, thepercentages of gravel and consolidated soil, coarse-grained soil, medium soil, fine-grainedsoil at different position of spoilbank slopes didn’t obviously change; Therefore, percentagesof material (particle diameter<10mm) at different position of spoilbank slopes can’t beconsidered during the design of the spoil underlying surface for laboratory rainfall simulation.(3) Based on the results of laboratory tests, the theory of statistica was applied to analyzeshape factors of slope. The results showed as follows: The gradient of spoilbank werebetween26°and35°in Dongbei plain, Huanghuaihai plain, Guanzhong plain, Qinbamountain area, red soil hilly region of Jiangxi, mountain area of Guizhou, with contributionrate61.4%,88.2%,90.2%,88.8%,70.8%,75.4%respectively.The slope length of spoilbank were between2m and8m in Dongbei plain, Huanghuaihaiplain, Guanzhong plain, Qinba mountain area, red soil hilly region of Jiangxi, with contribution rate82.5%,90%,100.0%,79.4%,70.5%respectively; The slope length ofspoilbank were longer than8m in mountain area of Guizhou with contribution rate80.0%.Therefore, intervals of gradient and length were mainly considered during design experimentof the spoilbank underlying surface in laboratory rainfall simulation.(4) The soil erosion and sediment yield process of different types were simulated ininner-door rainfall experimental condition. The results showed as follows: The infiltrationrate and sediment concentration of all spoilbanks decreased in a fluctuating tendency with therainfalls time, while the runoff rate increased in a fluctuating tendency with the rainfalls time,the variation of erosion sediment and transport rate appeared in two types with the rainfallstime, which were smooth and multimodal distribution.Runoff generation time had negative exponent relation to rainfall intensity, averageinfiltration rate. rainfall intensity had linear function of average runoff rate, average erosionsediment and transport rate respectively, average sediment concentration had exponentrelation to rainfall intensity, while total sediment yield and runoff volume accorded withlinear correlation.The type of rolling compaction by construction machinery at the top of slope showeddifferent characteristics of runoff and sediment yield from other types, which had the shortestrunoff generation time and lowest average infiltration rate in all design condition of rainfallintensity; The total sediment yield increased2.58times with rainfall intensities increasingfrom1.5to2.0mm/min. Under the rainfall intensity with2.0,2.5mm/min, the averagesediment ratio of runoff and average erosion sediment rate were higher than that of otherspoilbanks with significant difference (P<0.05).Therefore, appropriate measures of soil andwater conservation should be taken for this type of spoilbank in engineering practice, toreduce the harmful influence of soil and water erosion; The type of rolling compaction shouldbe distinguished from the other types when analysing and discussing in experimental study. |
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